Apparatus for developing photocopies by heat



Oct. 19, 1965 K. MUNNICH 3,213,256

APPARATUS FOR DEVELOPING PHOTOCOPIES BY HEAT Filed April 24, 1965 Fig. 44 2 Jnvenfor: (m-1 Hanan Mud-nu 4 Hu United States Patent 3,213,256APPARATUS FOR DEVELOPING PHOTOCOPIES BY HEAT Karl Miinnich, Siegen,Germany, assignor to Meteor Apparatebau Paul Schmeck G.m.b.H., Siegen,Westphalia, Germany Filed Apr. 24, 1963, Ser. No. 275,436

Claims priority, application Germany, Apr. 27, 1962,

M 52,659 7 Claims. (Cl. 21910.61)

The invention relates to an apparatus for developing photocopies byheat, wherein the photocopy is held in contact with a heat vehicle by amoving endless belt.

Photocopying papers are known which are developed solely by the actionof a heat after exposure. To obtain a uniform development for suchpapers the paper must be heated quite uniformly.

Known apparatus for developing such photocopying papers comprises aheatable roller used as a heat vehicle, and an endless heat-resistantbelt which is controlled by reversing rollers, moves across the surfaceof the roller, and moves the print over the roller while holding it incontact therewith. The belt may be divided up into adjacent narrowstrips if desired. The roller is heated by internal or external heatingsources, the heat of which is stored by the roller and then yielded tothe photocopying paper by conduction.

The known apparatus only imperfectly satisfies the requirement ofuniform heating of the photocopying paper. For the paper to be uniformlyheated throughout, the roller itself must be heated quite uniformly.This is difiicult to achieve with rotatable rollers, particularly if thepapers to be developed are very wide. There is generally a temperaturedrop towards the ends of the roller so that the paper is lessintensively developed at those places.

In addition, the heat transfer depends on the uniformity of contactbetween the roller and the paper. This necessitates very accuratemachining of the roller surface, and this is expensive. Even if theroller surface is completely uniform, it is diflicult to keep thephotocopying paper in uniform contact with the roller throughout bymeans of an endless belt.

The object of the invention is to provide an apparatus in which the saiddifliculties are extensively obviated.

To this end, according to the invention, the heat ve- 'hicle has atleast one fixed contact surface which forms part of a cylindricalsurface and over the convex side of which the endless belt moves.

The fixed contact surface in the apparatus according to the inventioncan be made uniformly much more easily and cheaply than a rotatableroller. Moreover, the fixed contact surface can be heated uniformly muchmore satisfactorily than with a rotating roller.

It should be noted that the term cylinder as used in this context doesnot necessarily mean a circular cylinder. The cross-section of thecontact surface perpendicular to the axis of the cylinder may thereforehave any convex curved shape, for example be parabolic. It is onlynecessary that all the planes containing the cylinder axis should cutthe contact surface at an axis-parallel straight line.

It is extremely simple to heat the heat vehicle if the latter consistsof a metal plate bent to be partly cylindrical. The plate can then be soconnected in a lowtension high-current circuit as to be heated byresistance heating.

Another possibility of heating the plate is for the plate to form thesecondary part of an induction heating system.

Resistance heating and induction heating may also be usedsimultaneously.

Examples of embodiment of the invention are illustrated in the drawingwherein: I

FIG. 1 is a diagrammatic section through an arrangement showing thebasic principle of the invention.

FIG. 2 is an example of the induction heating of the heat vehicle.

FIG. 3 is a cross-section through the arrangement shown in FIG. 2, takenalong lines A-A.

FIGS. 4 to 6 are diagrammatic sections of various embodiments of theapparatus.

The development apparatus shown in FIG. 1 comprises a heat vehicle 1with a convex contact surface over which an endless belt 2 passes. Thecontact surface forms a part of a cylindrical surface the axis of whichis perpendicular to the drawing plane, so that the belt bears closelyagainst the contact surface over the entire width transversely to thedirection of movement of said belt. The cylinder naturally need not be acircular cylinder but may have any cross-section. The only importantpoint is that the contact surface generatrices perpendicular to thedrawing plane should be straight.

The conveyor belt 2 is guided by an adjustable tensioning roller 3, areversing roller 4, and a driven conveyor roller 5. The photocopyingpaper to be developed is introduced between the belt 2 and the heatvehicle 1 in the direction of the arrow on the right-hand side of theapparatus in the drawing. The friction between the conveyor belt 2 andthe paper is much greater than the friction between the paper and thecontact surface so that the paper is driven by the conveyor belt. At thesame time it is held in close and uniform contact throughout with thecontact surface of the heat vehicle 1 so that there is a uniform heattransfer by which the paper is developed until it finally leaves theapparatus on the lefthand side in the drawing. During the passagethrough the apparatus, the exposed side of the paper may face theconveyor belt or the contact surface.

Possible means of heating the heat vehicle are shown in FIGS. 2 and 3.The vehicle consists of a bent plate 14 which is endless and whichsurrounds one arm of a magnet core 13, the other arm of which carries aprimary winding 15. In this case the plate 14 forms a shortcircuitedsecondary winding of the transformer so that after application of anA.C. voltage to the primary winding 15 currents are induced in the plate14. These currents very uniformly and rapidly heat the plate 14 and thetemperature can be controlled by tappings 16 on the primary winding 15.

Resistance heating and induction heating may naturally be appliedsimultaneously.

The endless belt and the conveying, reversing and tensioning rollers 3,4 and 5 are preferably also heated. This may be done by resistance orinduction heating as well. FIG. 1 shows another possibility of heatingthe conveyor belt. To this end, heater elements 17 are disposed on theback of the conveyor belt and their heat radiation is directed to theconveyor belt. A reflector 18 concentrates the radiant energy of theheater elements 17 onto the belt.

FIG. 4 shows another embodiment of the development apparatus wherein theheat vehicle 19 has a substantially parabolic cross-sectionperpendicularly to the cylinder axis, The advantage of this constructionis that the developed papers leave the apparatus on the same side asthey were introduced. This facilitates operation of the apparatus. Theconstruction of the endless belt 2 and rollers 3, 4 and 5 is the same asin FIG. 1. The heating vehicle 19 may be heated by one or more of thepossibilities explained with reference to FIGS. 1 to 3.

In the embodiment shown in FIG. 5, the heat vehicle 20 has two contactsurfaces 21 and 22 disposed substantially" parallel or at an acute angleto one another. A reversing roller 23 is disposed along the edge Wherethe two contact surfaces abut. This construction gives the sameadvantage as FIG. 4, namely, that the paper enters and leaves theapparatus on the same side, with a lower overall height.

The same effect is obtained with the arrangement shown in FIG. 7, inwhich the heat vehicle 24 comprises two facing contact surfaces 25 and26. The endless belt 2 runs without any additional tensioning orreversing rollers 2 between the two conveyor rollers 4 and 5, each runof the conveyor belt co-operating with a contact surface. The conveyorroller 5 inside the apparatus is surrounded by a reversing chute 27which guides the paper leaving the contact surface 25 to the contactsurface 26. In this case the conveyor roller 4 is both the inlet andexit roller.

In all the embodiments illustrated and described the conveyor belt mayconsist either of a single web extending over the entire width of thecontact surface or a number of parallel belts disposed side by side.

I claim:

1. An apparatus for developing photocopies by heat, comprising astationary heating member having a convex contact surface which formspart of a cylindrical surface, induction heating means arranged to heatsaid stationary heating member by electrical induction, an endless belt,means for moving said endless belt over said convex contact surface incontact therewith, and means for introducing the photocopies to bedeveloped between said convex contact surface and said endless belt.

2. The apparatus as defined in claim 1, wherein the cross-section ofsaid convex contact surface perpendicular to the cylinder axis issubstantially parabolic.

3. An apparatus for developing photocopies by heat, comprising anendless bent plate having a convex contact surface which forms part of acylindrical surface, a magnetic core having an arm extend-ing throughsaid endless bent plate, and a further arm carrying a primary windingconnected to an alternating voltage source, said endless bent plateforming a short-circuited secondary winding on said magnetic core, anendless belt, means for moving said endless belt over said convexcontact surface in contact therewith, and means for introducing thephotocopies to be developed between said contact surface and saidendless belt.

4. The apparatus as defined in claim 3, wherein the cross-section ofsaid convex contact surface perpendicular to the cylinder axis issubstantially parabolic,

5. An apparatus for developing photocopies by heat, comprising astationary heating member having two oppositely facing convex contactsurfaces, each of which forms part of a cylindrical surface, inductionheating means arranged to heat said stationary heating member byeletrical induction, an endless belt, means for moving said endless beltover said convex contact surfaces in contact therewith, and means forintroducing the photocopies to be developed between one of said convexcontact surfaces and said endless belt.

6. An apparatus for developing photocopies by heat, comprising astationary heating member having two spaced convex contact surfacesfacing each other, each of said contact surfaces forming part of acylindrical surface, induction heating means arranged to heat saidstationary heating member by electrical induction, an endless belt,means for moving said endless belt over said cont-act surfaces incontact therewith, and means for introducing the photocopies to bedeveloped between one of said contact surfaces and said endless belt.

7. An apparatus for developing photocopies by heat, comprising astationary heating member having a parabolic cont-act surface whichforms part of a cylindrical surface; induction heating means arranged toheat said stationary heating member; an endless belt; means for movingsaid belt over said parabolical contact surface while in contacttherewith; and means for introducing the photocopies to be developedbetween said convex contact surface and said endless belt.

References Cited by the Examiner UNITED STATES PATENTS 1,575,366 3/26Johnson 34233 1,701,156 2/29 Heritage 21910.61 2,994,134 8/61 Adams34-145 3,000,106 9/61 Christgau 219-383 X RICHARD M. WOOD, PrimaryExaminer.

1. AN APPARATUS FOR DEVELOPING PHOTOCOPIES BY HEAT, COMPRISING ASTATIONARY HEATING MEMBER HAVING A CONVEX CONTACT SURFACE WHICH FORMSPRT OF A CYLINDRICAL SURFACE, INDUCTION HEATING MEANS ARRANGED TO HEATSAID STATIONARY HEATING MEMBER BY ELECTRICAL INDUCTION, AN ENDLESS BELT,MEANS FOR MOVING SAID ENDLESS BELT OVER SAID CONVEX CONTACT SURFACE INCONTACT THEREWITH, AND MEANS FOR INTRODUCING THE PHOTOCOPIES TO BEDEVELOPED BETWEEN SAID CONVEX CONTACT SURFACE AND SAID ENDLESS BELT.